The potential for major extrapolation of creep rupture and creep strain data

Abstract Low stress interrupted creep test, as an interim compromise, can provide essential data for creep deformation design. However, there are no clear guidelines on the characterization of the terminating time for interrupted low-stress creep test. To obtain a suitable terminating time in terms of economy and effectiveness, long-term creep strain data of 9%Cr steels are collected from literatures and their creep deformation characterization is analyzed. First, the variations of normalized time and strain of each creep stage with the stress level are discussed. Then, the effect of the terminating time on final fitted results of Norton–Bailey equation is estimated. Third, the relationship between demarcation points at different creep stages and minimum/steady-state creep rate is analyzed. The results indicate that when the creep rupture life is considered as an important factor for creep design, the tertiary creep stage is of greatest significance due to the largest life fraction and creep strain fraction at low stress level. However, the primary and secondary creep stages are of great significance for design due to their larger contribution to 1% limited creep strain. And the long-term secondary creep data could be extrapolated by combining the primary creep strain data obtained from interrupted creep tests with the time to onset of tertiary creep derived from a similar Monkman–Grant relationship.

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Extrapolation of Creep Strain Data for Pure Copper

Journal of Testing and Evaluation ◽

10.1520/jte12037j ◽

1999 ◽

Vol 27 (1) ◽

pp. 31 ◽

Cited By ~ 9

Author(s):

DR Petersen ◽

RE Link ◽

R Sandström

Keyword(s):

Creep Strain ◽

Pure Copper ◽

Strain Data

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Simulation of Creep Deformation and Rupture of Notched Bar Specimens of Grade 92 Steel

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2015-45252 ◽

2015 ◽

Cited By ~ 2

Author(s):

Haruhisa Shigeyama ◽

Yukio Takahashi ◽

Jonathan Parker

Keyword(s):

Creep Strain ◽

Creep Behavior ◽

Power Plants ◽

Thermal Power ◽

Failure Criteria ◽

Creep Rupture ◽

Creep Failure ◽

Creep Tests ◽

Round Bar ◽

Grade 92 Steel

Creep strain equations of Grade 92 steel which is used in boilers and piping systems of ultra-supercritical (USC) thermal power plants were developed based on the results of creep tests on smooth round bar specimens of three kinds of Grade 92 steels. In these equations, primary creep behavior was represented by a power-law and tertiary creep behavior was described by an exponential function. Creep parameters were determined as a function of creep rupture times which were calculated from stress and absolute temperature. Additionally, generalized creep failure criteria considering the multiaxial stress were established on the basis of results of creep tests on circumferentially notched round bar specimens. These creep strain equations and creep failure criteria were incorporated into finite element analysis software. Then, creep failure analyses were carried out and the resulting deformation behavior and rupture times were compared with the experimental results. Creep rupture lives were predicted with a good accuracy, within a factor of two in most cases.

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Small Two-Bar Specimen Creep Testing of Grade P91 Steel at 650°C

High Temperature Materials and Processes ◽

10.1515/htmp-2014-0188 ◽

2016 ◽

Vol 35 (3) ◽

pp. 243-252

Author(s):

Balhassn S. M. Ali ◽

Tom H. Hyde ◽

Wei Sun

Keyword(s):

Strain Rate ◽

Creep Strain ◽

Test Data ◽

Creep Test ◽

Uniaxial Stress ◽

Creep Rupture ◽

Creep Strain Rate ◽

P91 Steel ◽

Uniaxial Creep ◽

Rupture Data

AbstractCommonly used small creep specimen types, such as ring and impression creep specimens, are capable of providing minimum creep strain rate data from small volumes of material. However, these test types are unable to provide the creep rupture data. In this paper the recently developed two-bar specimen type, which can be used to obtain minimum creep strain rate and creep rupture creep data from small volumes of material, is described. Conversion relationships are used to convert (i) the applied load to the equivalent uniaxial stress, and (ii) the load line deformation rate to the equivalent uniaxial creep strain rate. The effects of the specimen dimension ratios on the conversion factors are also discussed in this paper. This paper also shows comparisons between two-bar specimen creep test data and the corresponding uniaxial creep test data, for grade P91 steel at 650°C.

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Predicting creep rupture from early strain data

Materials Science and Engineering A ◽

10.1016/j.msea.2008.04.106 ◽

2009 ◽

Vol 510-511 ◽

pp. 25-28 ◽

Cited By ~ 5

Author(s):

Stefan Holmström ◽

Pertti Auerkari

Keyword(s):

Creep Rupture ◽

Strain Data ◽

Early Strain

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Karakteristik Laju Regangan Melar pada Baja Tahan Karat Austenitic 316L

ROTASI ◽

10.14710/rotasi.19.4.201-205 ◽

2017 ◽

Vol 19 (4) ◽

pp. 201

Author(s):

I. M. W. Ekaputra ◽

Gunawan Dwi Haryadi

Keyword(s):

Strain Rate ◽

Creep Strain ◽

Creep Curve ◽

Regression Line ◽

Grain Boundary Sliding ◽

Creep Rupture ◽

Creep Mechanism ◽

Creep Strain Rate ◽

Diffusional Creep ◽

Secondary Stage

In this study, the creep strain rate characteristics of austenitic 316L stainless steel was investigated from the uniaxial creep-rupture test. The tests were conducted under various applied load levels with a constant temperature at 525oC. The creep exponent was obtained by applying a Norton’s law equation on a regression line of creep strain rate vs. stress curve. The steel clearly showed an instantaneous primary stage, following with the secondary and tertiary stages on the creep curve. It was found that the creep rupture time decreased systematically with an increase in the stress. The secondary stage of creep curve almost dominated the creep’s lifetime. Therefore, the creep strain rate was determined from the minimum strain rate on this stage. The obtained creep exponent indicated that the responsible creep mechanism was grain boundary sliding or diffusional creep mechanism

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Extrapolation of Creep Strain and Rupture Properties of 1/2 per Cent Cr, 1/2 per Cent Mo, 1/4 per Cent V Pipe Steel

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1970_185_036_02 ◽

1970 ◽

Vol 185 (1) ◽

pp. 285-299 ◽

Cited By ~ 2

Author(s):

W. M. Cummings ◽

R. H. King

Keyword(s):

Creep Strain ◽

Material Properties ◽

Pipe Steel ◽

Parametric Methods ◽

Time Estimates ◽

Rupture Data ◽

Strain Data ◽

Long Time ◽

Accuracy Of Prediction ◽

Rupture Properties

Both 1 per cent total plastic strain data and rupture data of up to 21 000 h duration are presented for 1/2 per cent Cr, 1/2 per cent Mo, 1/4 per cent V pipe steel. Four parametric methods commonly used for extrapolation purposes are assessed for their accuracy of prediction within the time covered by the present experimental data. The Manson-Haferd parameter, which emerged as the most satisfactory of the four, is used as the basis for the long-time estimates of material properties. Based on the full 1 per cent strain and rupture data, 10 000, 30 000 and 100 000 h predictions are compared with the current British Steelmakers' Creep Committee recommendations. The tendency of both the Larson-Miller and Orr-Sherby-Dorn parameters to provide optimistic estimates at longer times is again demonstrated, and while the Manson Generalized parameter fits the data excellently within the experimental range, it is shown that care is required in selecting values of parametric constants if instability is to be avoided. To meet the increasing need for long-time creep strain data, each individual creep curve is represented by a creep strain/time relationship.

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AGC 2 Irradiation Creep Strain Data Analysis

10.2172/1374497 ◽

2016 ◽

Author(s):

William E. Windes ◽

David T. Rohrbaugh ◽

W. David Swank

Keyword(s):

Data Analysis ◽

Creep Strain ◽

Irradiation Creep ◽

Strain Data

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Numerical Prediction of Creep Rupture Life of Ex-Service and As-Received Grade 91 Steel at 873 K

International Journal of Automotive and Mechanical Engineering ◽

10.15282/ijame.18.3.2021.01.0678 ◽

2021 ◽

Vol 18 (3) ◽

pp. 8845-8858

Author(s):

IMAM UL FERDOUS ◽

NASRUL AZUAN ALANG ◽

Juliawati Alias ◽

Suraya Mohd Nadzir

Keyword(s):

Finite Element ◽

Stress State ◽

Creep Strain ◽

Life Prediction ◽

Rupture Life ◽

Creep Rupture ◽

Rupture Time ◽

Damage State ◽

Grade 91 ◽

Grade 91 Steel

Infallible creep rupture life prediction of high temperature steel needs long hours of robust testing over a domain of stress and temperature. A substantial amount of effort has been made to develop alternative methods to reduce the time and cost of testing. This study presents a finite element analysis coupled with a ductility based damage model to predict creep rupture time under the influence of multiaxial stress state of ex-service and as-received Grade 91 steel at 873 K. Three notched bar samples with different acuity ratios of 2.28, 3.0 and 4.56 are modelled in commercial Finite Element (FE) software, ABAQUS v6.14 in order to induce different stress state levels at notch throat area and investigate its effect on rupture time. The strain-based ductility exhaustion damage approach is employed to quantify the damage state. The multiaxial ductility of the material that is required to determine the damage state is estimated using triaxiality-ductility Cock and Ashby relation. Further reduction of the ductility due to the different creep mechanisms over a short and long time is also accounted for in the prediction. To simulate the different material conditions: ex-service and as-received material, different creep coefficients (A) have been assigned in the numerical modelling. In the case of ex-service material, using mean best fit data of minimum creep strain rate gives a good life prediction, while for new material, the lower bound creep coefficient should be employed to yield a comparable result with experimental data. It is also notable that ex-service material deforms faster than as-received material at the same stress level. Moreover, higher acuity provokes damage to concentrate on the small area around the notch, which initiates higher rupture life expectancy. It also found out that, the stress triaxiality and the equivalent creep strain influence the location of damage initiation around the notch area.

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